The present invention relates to a process for finish-abrading an end-surface of optical fiber equipped with a ferrule, that is, an optical-fiber-connector end-surface.
Conventionally, an optical-fiber-connector which can be easily removed is widely used for connection of optical fibers in optical fiber communication network. In the connection at the optical-fiber-connector, end-surfaces of the optical-fiber-connector made of optical fiber and a covering portion (ferrule) for covering the optical fiber, are allowed to directly abut each other. Therefore, the optical characteristics at the time of connection, particularly connection loss, depend on the processing properties and precision of an optical-fiber-connector end-surface.
An optical-fiber-connector end-surface is processed through several abrasion steps. Usually, the steps of removing adhesives, abrading to curved surface, secondary-abrading, and finish-abrading are conducted. The finish-abrading means abrasion at the final stage conducted with using abrasive grains of the smallest size (a grain size of 5 to 1000 nm), thereby surface roughness Ra of not more than 5 nm is provided.
Quality of the optical-fiber-connector end-surface is influenced by processing properties and precision in the final finishing abrasion step. In other words, major factors for connection loss of the optical fiber are degree of finishing roughness of the end-surface and its inclination.
In the step of finish-abrading an optical-fiber-connector end-surface, superfine silica and the like was used as free abrasive grains in the past. However the process using free abrasive grains is complicated in work, so an abrasive film composed of abrasive grains fixed on a film-form substrate, is widely employed at present.
The abrasive grains are fixed by a binder, and an abrasive layer, which has abrasive grains and a binder, is usually formed on a film-form substrate. Finish-abrading of an optical-fiber-connector end-surface is conducted by applying the optical-fiber-connector end-surface to an abrasive surface of the abrasive film and rubbing with a predetermined amount of pressure.
Japanese Patent Laid-open Publication No. 248771/1997 discloses an abrasive tape for an optical-fiber-connector end-surface that has an abrasive layer containing abrasive grains and a binder on a substrate, the abrasive grains being silica particles having an average particle size of 5 to 30 nm. Japanese Patent Laid-open Publication No. 71572/1998 discloses an abrasive tape for optical fiber that has a primer layer and an abrasive layer containing abrasive grains and a binder on a substrate, the abrasive grains being alumina-silica composite particles having an average particle size of 10 to 700 nm.
However, when abrasive grains of fine size are employed, a long period of time for abrading is necessary. Further, an abrasive material of fine grade has a problem of loading. The term “loading” means that spaces between abrasive grains are filled with abrasion dusts that protrude to inhibit abrasive ability.
In case when an optical-fiber-connector end-surface is abraded by using an abrasive material of which surface is flat, particles of abrasion dusts stay between abrasive grains, thereby abrasive grains become poor in cutting ability. The abrasive material described in the above publications has a flat abrasive surface, and cutting ability easily decreases. Further, a liquid used as coolant or lubricant hardly works between an abrasive material and an optical-fiber-connector end-surface, a part of the abrasive layer adheres to an abraded surface of the optical-fiber-connector, and it is complicated in work for removing.
Japanese Patent Laid-open Publication No. 33372/1999 discloses an abrasive tape for an optical-fiber-connector end-surface which has an abrasive layer containing abrasive grains and a binder on a substrate, the abrasive grains being silica particles having an average particle size of 5 to 30 nm, the abrasive layer being formed with cracks of network structure, so that abrasion dusts can be recovered on the abrasive tape.
Japanese Patent Laid-open Publication No. 2001-179640 discloses an abrasive material for an optical-fiber-connector end-surface which has an abrasive layer containing abrasive grains and a binder on a substrate, the abrasive layer having three-dimensional structure constructed with a plurality of regularly arranged three-dimensional elements having a predetermined shape. The abrasive layer of such three-dimensional structure easily let abrasion dusts out, and is resistant to loading and excellent in durability. Further, a smear hardly adheres on an abraded surface, and frequency in generation of abrasion scratch is also very low.
However, in order to control generation of abrasion scratch more effectively, silica particles have to be used as abrasive grains, particle size have to be made small, and a binder contained in an abrasive layer have to be made soft. Although generation of abrasion scratch was effectively controlled in this case, it was newly discovered that adherent substance was generated on an abraded surface of optical fiber with certain frequency.
If the adherent substance on an abraded surface of optical fiber is left as it is, connection loss becomes large, whereas a cleaning step for removing it, results in additional labor. Therefore, it is generally desired a process for finish-abrading an optical-fiber-connector end-surface without generating abrasion scratch on an abraded surface of optical fiber, nor generating adherent substance.
The present invention has been made to solve the aforesaid problems of the prior art and an object thereof is to provide a process for finish-abrading an optical-fiber-connector end-surface without generating abrasion scratch on an abraded surface of optical fiber, nor generating adherent substance.